knot-dns-users October 2020

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dynamic updates (DDNS)

by Thomas

Hi! Is it safe to mix dynamic updates and manual editing of a zone? Thanks! Thomas

5 years, 1 month

Inter-operability issues with other DNS Servers

by Evilham

Ahoj, I've searched through the archives and read documentation+RFCs to no avail, so I hope you can help out. I run the authoritative DNS servers for an associative ISP in Barcelona (eXO.cat), and we are running them in FreeBSD using Knot DNS (2.9.5, but .6 and .7's changelogs do not point to a similar issue being solved). We have since then gotten a few reports from different parties of "DNS issues", I am reasonably sure to have pinpointed this down to badly configured DNS resolvers, but our weight is really too tiny to force any change; and the doubt remains as to whether or not this is on us. Without access to the resolvers it's also a tad tricky for us to reproduce. Things do work beautifully with pretty much all of the internet. This appears to be related to: https://tools.ietf.org/html/rfc7873#section-5.2.3 (sometimes in connection with 5.2.4) Maybe someone with more experience and running at a larger scale has pointers on this topic. Specifically, I have observed: Case A: 1. (Probably Bind) Resolver contacts Knot DNS with Client Cookie and old Server Cookie 2. Knot DNS responds BADCOOKIE with the provided Client Cookie, Old Server Cookie, and adds the new server cookie. 3. Resolver contacts Knot DNS with the same Client Cookie and old Server Cokie 4. 2 and 3 repeat for a long time. 5. Domains end up not resolving. Case B: https://github.com/matrix-org/synapse/issues/8581 Their supplier says the DNS server "replies with BADCOOKIE to UDP queries", as if that were a bad thing; but from reading RFC7873, I understand that it is expected documented behaviour and the client ought to try again with the given Server Cookie. They say: "AIUI the resolver does retry, but again receives a BADCOOKIE response." I sadly don't have the tcpdump for those, but it could be just like case A again. These are the relevant bits from the config: server: rundir: "/var/run/knot" user: knot:knot listen: [ 0.0.0.0@53, ::@53 ] log: - target: syslog any: info statistics: append: off database: storage: "/var/db/knot" mod-cookies: - id: default badcookie-slip: 1 mod-rrl: - id: default rate-limit: 200 # Requests per second template: - id: default storage: "/var/db/knot/primary" semantic-checks: on disable-any: on serial-policy: dateserial file: "%s.zone" global-module: mod-cookies/default global-module: mod-rrl/default global-module: mod-stats - id: secondary storage: "/var/db/knot/secondary" semantic-checks: on disable-any: on serial-policy: dateserial file: "%s.zone" module: mod-cookies/default module: mod-rrl/default module: mod-stats - id: signed storage: "/var/db/knot/primary" dnssec-signing: on zonefile-load: difference semantic-checks: on disable-any: on serial-policy: dateserial file: "%s.zone" module: mod-cookies/default module: mod-rrl/default module: mod-stats We are not using anycast clusters or anything like that. A quick solution would be to disable cookies or to experiment with noudp, but that's something we'd like to avoid. The name servers in question are: - ns3.exo.cat - ns4.exo.cat - ns1.unchat.cat (not association, but identical setup) All tests I've ran against the servers and the associated domains (e.g. exo.cat + unchat.cat) appear to be fine. There is an odd one with https://dnsviz.net/d/unchat.cat/dnssec/, but other tests like https://www.zonemaster.net/result/d530cb253298b56c do not report any issues. Thank you in advance for any pointers you may have (and for Knot DNS!), -- Evilham

5 years, 1 month

Knot upgrade

by Oto Stefan

Hallo everybody, this is just a little remark concerning the 'knot' upgrade from 2.9.x to 3.0.x. The 'update-owner-name' in the 'acl' section of the configuration file can now be either the FQDN (with trailing dot) or a relative name to the zone, while it used to be a domain name before (without obligatory dot at the end). The documentation was updated correctly: Doc for 2.9: acl - id: owner_type_rule action: update update-type: [A, AAAA, MX] # Updates are only allowed to update records of the specified types update-owner: name # The allowed owners are specified by the list on the next line update-owner-name: [a.example.com, b.example.com, c.example.com] update-owner-match: equal # The owners of records in an update must be exactly equal to the names in the list Doc for 3.0: acl - id: owner_type_rule action: update update-type: [A, AAAA, MX] # Updates are only allowed to update records of the specified types update-owner: name # The allowed owners are specified by the list on the next line update-owner-name: [a, b.example.com.] # Non-FQDN names are relative to the effective zone name update-owner-match: equal # The owners of records in an update must be exactly equal to the names in the list However; I did not notice the subtle change and was struggling for a while to bring the dynamic zone update into a working state again . Maybe, this saves a little time to someone else. Regards and thanks for a great piece of software, Oto Stefan

5 years, 1 month

Warning - TCP ports binding in Knot DNS versions 3.0.0 and 3.0.1

by David Vasek

Hello Knot DNS users! We would like to inform you about a change in Knot DNS behaviour in versions 3.0.0 and 3.0.1. These two versions don't allow sharing of TCP ports between programs, including other knotd instances (SO_REUSEADDR isn't set). While this behaviour is better from point of view of security, the downside of it is that when restarting a knotd daemon, binding to a TCP port may fail after a restart if the restart is immediate. In such a case, an error is logged and Knot starts its operation on other configured ports only. To verify that all TCP ports have been bound successfully after Knot restart, please always check the log for possible errors. Such errors would be close to the initial message about Knot DNS starting. Since there was a complaint about this change, we plan to re-enable TCP ports reuse in future releases. We also ponder making knotd exit if it fails to bind to any of configured TCP ports. We would like hear from you whether such a behaviour is what you, users, want best. Please, let us know if you prefer this or a different solution. With regards, David Vašek CZ.NIC

5 years, 1 month

Knot DNS 3.0.1 release

by Daniel Salzman

Hello Knot DNS users, CZ.NIC has released Knot DNS 3.0.1! It's recommended to update from 3.0.0 version if you serve DNSSEC signed zones with NSEC3. Changelog: https://gitlab.labs.nic.cz/knot/knot-dns/raw/v3.0.1/NEWS Download: https://www.knot-dns.cz/download/ Documentation: https://www.knot-dns.cz/docs/3.0/html Support and sponsorship: https://www.knot-dns.cz/support Regards, Daniel

5 years, 2 months

Knot DNS 2.9.7 release

by Daniel Salzman

Hello Knot DNS users, CZ.NIC has released Knot DNS 2.9.7! This is a bugfix version of previous stable branch. It's recommended to update from older 2.9.x versions if you serve DNSSEC signed zones with NSEC3. Knot DNS 3.0.1 will be released tomorrow. Changelog: https://gitlab.labs.nic.cz/knot/knot-dns/raw/v2.9.7/NEWS Download: https://www.knot-dns.cz/download/ Documentation: https://www.knot-dns.cz/docs/2.9/html Support and sponsorship: https://www.knot-dns.cz/support Regards, Daniel

5 years, 2 months

Debugging high CPU / Load - normal?

by Jonathan Hewlett

Hi, We run around 50 knot servers around the world, with great success - thanks for the software! We are just a little curious about seemingly high CPU usage, and how best to interpret the results, if someone could advise? Specifically, we are seeing the majority of the cpu time in 'system' and not 'user', what would that suggest is happening perhaps? Any tuning help gratefully received! Our platform (sample) 24 Core CPU E5-2440 0 @ 2.40 64Gb RAM SSD knot-2.9.5, running on Centos 8.2 Currently receiving around 4k pps Server is authoritative for a 278 zones, the largest zone file being around 600Mb Output of top top - 20:50:38 up 6 days, 4:49, 2 users, load average: 13.47, 12.34, 11.83 Tasks: 321 total, 2 running, 318 sleeping, 0 stopped, 1 zombie %Cpu0 : 4.0 us, 34.1 sy, 0.0 ni, 60.3 id, 0.3 wa, 0.7 hi, 0.7 si, 0.0 st %Cpu1 : 4.3 us, 19.4 sy, 0.0 ni, 75.3 id, 0.0 wa, 0.3 hi, 0.7 si, 0.0 st %Cpu2 : 4.3 us, 33.8 sy, 0.0 ni, 60.9 id, 0.0 wa, 0.7 hi, 0.3 si, 0.0 st %Cpu3 : 5.0 us, 21.2 sy, 0.0 ni, 73.2 id, 0.0 wa, 0.3 hi, 0.3 si, 0.0 st %Cpu4 : 3.3 us, 34.9 sy, 0.0 ni, 61.5 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu5 : 3.0 us, 20.2 sy, 0.0 ni, 76.2 id, 0.0 wa, 0.3 hi, 0.3 si, 0.0 st %Cpu6 : 4.0 us, 35.2 sy, 0.0 ni, 60.4 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu7 : 5.0 us, 18.7 sy, 0.0 ni, 76.0 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu8 : 2.0 us, 35.0 sy, 0.0 ni, 62.3 id, 0.0 wa, 0.7 hi, 0.0 si, 0.0 st %Cpu9 : 2.0 us, 20.0 sy, 0.0 ni, 77.7 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu10 : 3.7 us, 34.4 sy, 0.0 ni, 61.2 id, 0.0 wa, 0.7 hi, 0.0 si, 0.0 st %Cpu11 : 3.3 us, 20.7 sy, 0.0 ni, 75.7 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu12 : 2.3 us, 34.6 sy, 0.0 ni, 62.1 id, 0.0 wa, 0.7 hi, 0.3 si, 0.0 st %Cpu13 : 3.3 us, 20.7 sy, 0.0 ni, 75.7 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu14 : 2.3 us, 33.6 sy, 0.0 ni, 59.7 id, 0.0 wa, 0.7 hi, 3.7 si, 0.0 st %Cpu15 : 3.3 us, 19.7 sy, 0.0 ni, 76.3 id, 0.0 wa, 0.3 hi, 0.3 si, 0.0 st %Cpu16 : 2.3 us, 34.0 sy, 0.0 ni, 58.7 id, 0.0 wa, 1.0 hi, 4.0 si, 0.0 st %Cpu17 : 2.3 us, 21.5 sy, 0.0 ni, 75.8 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st %Cpu18 : 3.3 us, 34.8 sy, 0.0 ni, 57.2 id, 0.0 wa, 0.7 hi, 4.0 si, 0.0 st %Cpu19 : 5.0 us, 19.3 sy, 0.0 ni, 75.1 id, 0.0 wa, 0.3 hi, 0.3 si, 0.0 st %Cpu20 : 2.7 us, 35.3 sy, 0.0 ni, 60.0 id, 0.0 wa, 0.7 hi, 1.3 si, 0.0 st %Cpu21 : 1.7 us, 20.5 sy, 0.0 ni, 77.2 id, 0.0 wa, 0.3 hi, 0.3 si, 0.0 st %Cpu22 : 4.7 us, 32.4 sy, 0.0 ni, 58.5 id, 0.0 wa, 0.7 hi, 3.7 si, 0.0 st %Cpu23 : 2.3 us, 19.0 sy, 0.0 ni, 78.3 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st MiB Mem : 64107.4 total, 46764.9 free, 11733.6 used, 5608.8 buff/cache MiB Swap: 32248.0 total, 32248.0 free, 0.0 used. 51670.0 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 213370 knot 20 0 34.0g 9.6g 41784 S 644.9 15.3 1319:12 /usr/sbin/knotd Thanks again for this great product. Jonathan

5 years, 2 months

Catalog zone configuration/zone auto configuration bootstrapping

by Frank Matthieß

Hello all, i stuck a little bit with the configuration of the new catalog zone feature in knot dns 3.0.0. The catalog zone replication is running quite well, but bootstrapping this feature to replicate the config for zones wont work for me. The zone name of the catalog zone is "zone.catalog". The primary name server uses this config: > # Configuration export (Knot DNS 3.0.0) > zone: > - domain: "zone.catalog." > file: "%s" > notify: [ "ns1.frank.REDACTED.DOM", "ns2.frank.REDACTED.DOM" ] > acl: [ "ns1.frank.REDACTED.DOM", "ns2.frank.REDACTED.DOM" ] > catalog-role: "interpret" > catalog-template: "catalog-zone-template" > > - domain: "dom-siew9tho.invalid." The zone has this content: > [zone.catalog.] zone.catalog. 60 NS nshp.frank.REDACTED.DOM. > [zone.catalog.] zone.catalog. 60 SOA nshp.frank.REDACTED.DOM. hostmaster.REDACTED.DOM. 1601540072 16384 2048 1048576 2560 > [zone.catalog.] id-ies3eidiev4ooquahgoh.zone.catalog. 0 PTR dom-siew9tho.invalid. > [zone.catalog.] version.zone.catalog. 0 TXT "2" Adding the following config to the primary works: > conf-begin > conf-set zone.domain "dom-siew9tho.invalid." > conf-commit > zone-begin dom-siew9tho.invalid. > zone-set dom-siew9tho.invalid. @ 60 SOA nshp.frank.REDACTED.DOM. hostmaster.REDACTED.DOM. 1 16384 2048 1048576 2560 > zone-set dom-siew9tho.invalid. @ 60 NS nshp.REDACTED.DOM. > zone-commit dom-siew9tho.invalid. Query one of the secondaries (ns1) gives me: > error: (no such zone found) [dom-siew9tho.invalid.] The config of ns1: > # Configuration export (Knot DNS 3.0.0) > template: > - id: "catalog-zone-template" > storage: "/var/lib/knot/zones" > file: "%s" > semantic-checks: "on" > dnssec-signing: "off" > serial-policy: "unixtime" > kasp-db: "/var/lib/knot/kasp-db" > > zone: > - domain: "zone.catalog." > file: "%s" > master: "nshp.frank.REDACTED.DOM" > acl: "nshp.frank.REDACTED.DOM" > catalog-role: "interpret" > catalog-template: "catalog-zone-template" I'm sure i miss one or more parts and/or i have a serious misunderstanding of the bootstrapping setup for this feature. - frank -- Frank Matthieß Mail: frank.matthiess(a)virtion.de phone: +49 521 44 81 58 17 GnuPG: 9F81 BD57 C898 6059 86AA 0E9B 6B23 DE93 01BB 63D1 virtion GmbH Südring 11, DE 33647 Bielefeld Geschäftsführer: Michael Kutzner Handelsregister HRB 40374, Amtsgericht Bielefeld, USt-IdNr.: DE278312983

5 years, 2 months

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knot-dns-users October 2020